<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>盒子模型之边框</title>
  
</head>
<style>
    div {
           width: 200px;
           height: 200px;
           /* border-width 边框的粗细  一般情况下都用px */
           /* border-width: 5px; */
           /* border-style 边框的样式 solid 实线边框 */
           /* border-style: solid; */
           /* border-style 边框的样式 dashed 虚线边框  dotted 点线边框*/
           /* border-style: dashed; */
           /* border-style: solid; */
           /* 设置边框颜色 */
           /* border-color: violet; */
           /* 简洁语句  */
           border: 2px solid blue;
           /* 单独设置上边框 */
           border-top: 5px dotted red;
       }
</style>
<body>
    <div></div>
</body>

</html>